Merge pull request #1695 from progit/dependabot/bundler/epubcheck-ruby-4.2.6.0

Update epubcheck-ruby requirement from 4.2.5.0 to 4.2.6.0

Author: ben

Gemfile

@@ -12,6 +12,6 @@ gem 'asciidoctor-pdf', '1.6.0'
 gem 'coderay', '1.1.3'
 gem 'pygments.rb', '2.2.0'
 gem 'thread_safe', '0.3.6'
-gem 'epubcheck-ruby', '4.2.5.0'
+gem 'epubcheck-ruby', '4.2.6.0'
 gem 'html-proofer', '3.19.2'
 gem 'kindlegen', '3.1.1'